What Are Effective Internal Combos for Stock Clip Dirt Racing Engines?

[BT21]

Hi there all, Big fan of the site and info provided. I stumbled onto it just looking for general info and perhaps some up to date opinions on suspenion for stock clip applications for dirt racing. I have been in the industry for some time, ie; NASCAR fabricator, DIRT chassis builder (NE mods as well as IMCA style open wheels) and metal fabricator in general. I supervise a production weld shop with robotics and hand welded jig applications so my mind is always turning. I spent most of my time on the rear end of the last few dirt cars I have been involved with and drove myself. The stock clip front end is a little taboo to me. Getting off track I will pick Ranger Mike's brain. However the common theme is the small block chevy power with a 500 lift at the valve flat tappet cam rule. With your background have you any thoughts on combinations of internals or lobe separation, etc. The last one we put together was a mild motor completely legal and made 460 HP and 450 Ft/lbs Torque. 355 cu in. I understand common trends, lighter rotating assemblies, deccking the block and heads but just thought I would ask if there was anything you have picked up on or thought would work. If need be I can provide more details in regards to rule specs. Pretty straight forward though. 23 degree heads, 2.02 and 1.60 valves, 750 max carb (1), stock rod length for make 5.7 and stock replacement crank no knife edging or holes in throws and flat top pistons. Some other track a little different but this combo allows for legality across at least 5 tracks.

Again first time writing and think its great. Look forward to reading more!

 

[Ranger Mike]

Hello BT...nice to hear from you..i currently run SCCA which is very restrictive. But as Smokey Yunick said..ifin it aint in the rule book it is legal...that said , you can get SIGNIFICANT power by re-grinding your cam with different lobe separation angle. This was done regularly in NASCAR back in the Hemi and Ford engine of the week days. I did it and it makes a difference!. Also the use of electric water pump and fuel pump will give extra horsepower. The fuel pump has to be wired to shut off in event of impact though..naturally. Look at reducing the crank and rod bearing widths as the stock specs are way over kill. When we ran the small block Chevy we had 5.7 rods or longer as you only need 0.100" top piston land width and we ran smallest diameter wrist pins we could get. Super skinny rings too. We found the timing chain is parasitic so belt is only way to go hp wise, never gears. Oil control is huge as the oil is like taffy and really sucks HP so control your clearances. I love Blockrete and always put 3/4" of it in block to tie in the bottom of the cylinders. They do flex and anything you can do to stabilze the engine at 7000 RPM is a plus. You don't want to use a lot as you need to cool off the cylinder at the top via oil splash from the crank but you only need three inches of bare metal for this. Make sure you re-plumb the oil system as the old chevy blocks never did oil the rear main bearing with FILTERED oil. Plumb an oil line to the top front lifter gallery to slow down the oil coming from the pump. It can speed past the lifters and cause the front rod bearings to starve. Avoid any 90 degree corners like the plauge and do your best to radius and in the block. One final thought..750 cfm carb is plenty but take the time and money to wet flo bench the manifold and head. Make sure yo u get the most trick tulip intake valves you can afford. Get a checker!
rm